Overall, more than 82 percent of Americans have a religious identity, with this breakdown:

• Protestant/other Christian: 52.5 percent.

• Roman Catholic: 23.6 percent.

• Mormon: 1.9 percent.

• Jewish: 1.6 percent.

• Muslim: 0.5 percent.

• Other non-Christian religion: 2.4 percent.

• None/atheist/agnostic: 15 percent.

• No response: 2.5 percent.

The findings fit the trend of an increasing percentage of Americans who don't embrace a formal religious identity. In 1951, 1 percent of Americans didn't have a religious identity, compared to 24 percent identifying as Roman Catholic and 68 percent claiming a non-Roman Catholic Christian faith.

Earlier in 2011, Gallup found that 92 percent of Americans say they believe in God, which suggests that a lack of religious identity is not necessarily linked to atheism.